A spray gun (dispensing apparatus) presently in use and similar in many general respects to the gun of the instant invention is disclosed in U.S. Pat. Nos. 3,900,163 and other pertinent dispensing apparatuses are disclosed in U.S. Pat. Nos. 3,920,188, 3,717,306, 3,087,682, 3,235,186, 3,240,432, 3,399,837, 3,504,855, 3,587,970, 3,606,170, 3,687,370, 3,708,123, 3,837,575 and 3,958,757.
These various dispensing apparatuses are for the most part designed to mix and spray discharge a plurality of fluent materials and each is particularly well adapted, in at least certain manners, to mix and spray discharge the particular types of fluent materials for which these dispensing apparatuses have been designed to handle. Those dispensing apparatuses designed to mix and spray discharge two or more chemically reactive fluid components, for various reasons, are not fully dependable in operation, without extensive maintenance, for the purpose of mixing and spray discharging A and B components of urethane foam plastic. Accordingly, a need exists for an efficient urethane foam plastic spray gun which will be efficient in performing its intended function and which will have an extended operational life independent of more than minimal maintenance.